Motorized apparatus for opening and closing sectional overhead doors has long been known in the art. These powered door operators were developed in part due to extremely large, heavy commercial doors for industrial buildings, warehouses, and the like where the opening and closing of the doors essentially mandated power assistance. Eventually, homeowner demands for the convenience and safety of door operators, particularly when remote actuation became readily feasible, resulted in an extremely large market for powered door operators for residential applications.
The vast majority of motorized operators for residential garage door applications employ a trolley-type system extending perpendicular to the door header into the garage to apply force to a section, normally the upper section, of the door for powering between the open and closed positions. Another type of motorized operator is known as a "jack-shaft" operator, which is used extensively in commercial applications and is so named by virtue of similarities with transmission devices where the power or drive shaft is parallel to the driven shaft, with the transfer of power occurring mechanically as by gears, belts, or chains interconnecting the drive shaft and a driven shaft, which controls the position of a door.
The extensively employed door operators that connect directly to the garage door, principally the trolley-type systems, traditionally have a manual disconnect that at any time disconnects the operator from its mechanical interconnection with the door. These disconnects are usually incorporated into the trolley portion of the operator in such a fashion that when disconnected, the door is free to be manually moved in either the open or closed direction. This type of disconnect for trolley-type operators permit a person to isolate the arm interconnecting the door and the trolley in the event the operator or the door malfunctions, there is a loss of power to the operator, or the door entraps a person or object. A disconnect of this general type has been a mandatory requirement for trolley-type garage door operators for a number of years.
The disconnect handle on trolley-type operators is normally attached to a rope that is suspended from, and moves with, the trolley as the operator opens and closes the garage door. There are industry requirements that a handle be at the bottom of the rope suspended from the trolley and be suspended no more than six feet from the floor so that it is available to be grasped by a person and pulled to effect disconnect in the event of an emergency.
These positioning requirements coupled with the basic characteristics of a trolley-type system create serious disadvantages in some operating conditions. The fact that the rope and disconnect handle move with the trolley may undesirably make it difficult to locate the handle at night or in a dark garage when there is a power failure. In addition, the movement of the rope suspended handle into and out of the garage during opening and closing of the door can result in the handle dragging across the top of high vehicles and even becoming entangled in a luggage rack or other appurtenances that may be roof-mounted on vans or sports utility vehicles. It is also to be observed that when a garage door is closed, the disconnect rope and handle are in the closest proximity to the garage door. When the door has windows positioned in the top section of the door, as is customary, the security of the garage in regard to breaking and entering is seriously compromised. In such instance, if the center window pane is broken, the disconnect handle is within easy reach for an intruder to disconnect the door from the operator and subsequently manually open the door to the garage.
Most of the commercially-employed disconnects for trolley-type operators are weighted or spring-loaded toward the connected position, such that these biasing forces must be overcome to disengage the disconnect so the door can be moved independent of the trolley. This biasing allows the disconnect to automatically re-engage when the door is manually moved to the precise position where disengagement was effected by the disconnect. In some instances, disconnects automatically engage when the trolley is moved by the operator motor to the appropriate position for a current door location. While automatic engaging features are sometimes considered to be advantageous, in other instances a disconnect that engages only when a positive manual action, such as moving a handle or lever, is taken is preferred. While it is generally conceded to be highly advantageous to engage a disconnect at any location of the door and operator without adjusting the position of either, such an operational format is not possible with current trolley-type operator designs.
In relation to jack-shaft operators, the operator units are normally mounted on the side of the door outwardly of the rails, which can produce clearance problems in the instance of minimal clearance between a garage side wall and the rails for the door rollers. Whether of a vertical open position type door as is employed in commercial installations where there is substantial building height or a horizontal open position type door, as is necessary for most residential installations, disconnection of the motor and the door is normally effected by a rope and handle suspended either from the operator unit or by a lever or actuating arm located on the operator. In residential applications where there are top section windows, such disconnects are subject to forced entry by breaking an end window and merely pulling the disconnect handle or the disconnect lever. In instances where a jack-shaft operator may be mounted above the door, a serious operational deficiency is encountered in efforts to effect disconnect when the door is at an intermediate position because the portion of the door extending horizontally into the garage renders the operator and its disconnect mechanism above the door inaccessible in virtually all instances, except when the door is in the fully closed position. Thus, existing disconnects suffer from one or more disadvantageous characteristics.